Motor vehicles – Power – Having specific motor-to-body-frame relationship
Reexamination Certificate
1998-04-27
2001-07-17
Dickson, Paul N. (Department: 3618)
Motor vehicles
Power
Having specific motor-to-body-frame relationship
C180S309000, C060S322000
Reexamination Certificate
active
06260652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an exhaust system. The exhaust system is intended, for example, for a car but may also be used for another motor vehicle—for example a truck or bus. The internal combustion engine may consist of a gasoline or diesel engine.
2. Description of the Prior Art
The engine housing of the internal combustion engine of a motor vehicle is usually held on the vehicle body by retaining means in such a way that it is slightly mobile, elastically mounted and damped with respect to vibration. When the motor vehicle is used, rapid load changes and rapid changes in the speed of the engine shaft and/or of the torque output by said shaft cause rapid changes in the power of the internal combustion engine. These may in turn give rise to movements, namely approximately rotation and/or swivelling of the engine casing about a virtual axis of rotation and/or pivot axis. Furthermore, the internal combustion engine produces vibrations or oscillations of the engine casing. These may cause, inter alia, periodic swivelling back and forth or torsional oscillations about the virtual axis of rotation and/or pivot axis. The virtual axis generally does not coincide with the geometric axis of rotation of the engine shaft and is, for example, offset from the axis of rotation of the engine shaft and approximately parallel to said axis. In the case of the swivelling caused by power changes and/or by vibrations, the engine casing may be swivelled back and forth or rotated through angles which are, for example, up to about 5°.
Known exhausts have an exhaust section which is rigidly connected to the engine casing and is connected via a flexible pipe member to at least one catalytic converter and/or silencer arranged downstream of said pipe member and having a casing. If the exhaust section located downstream of a flexible pipe member contains a plurality of casings, a flexible pipe member is sometimes also arranged between the successive casings. The flexible pipe members have, for example, a bellows. The exhaust section located downstream of a flexible pipe member is usually held displaceably on the vehicle body by, for example, retaining means having rubber rings.
During operation, the exhaust section connected rigidly to the engine housing is concomitantly moved by the swivelling engine casing and, when connected to the (first) flexible pipe member, executes swivelling movements whose arc lengths are—depending on the distance from the virtual axis—for example several centimeters and cause considerable deformations of the bellows. When these movements occur, the distance of the entrance of the bellows from the (first) casing is usually changed. In general, the result of this is that the bellows is not only frequently bent but at the same time is also alternately compressed and extended and frequently also subjected to shear movements. Bellows may withstand a very large number of bending movements without damage. Furthermore, small changes in the length of the bellows are also permissible. However, length changes and especially shear movements occurring simultaneously with bending movements give rise to considerable stresses in the bellows and shorten their service life.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide an exhaust system which overcomes disadvantages of the known exhaust systems and in particular permits a long service life of the (first) flexible pipe member which follows, along the exhaust gas flow path, the exhaust section connected rigidly to the engine casing.
This object is achieved according to the invention by an exhaust system for a motor vehicle which has a vehicle body and an internal combustion engine with an engine casing and which has an exhaust connectable to the internal combustion engine and having a first flexible pipe member, a second flexible pipe member, connected to said first pipe member via a pipe, and at least one casing arranged downstream of said second pipe member and belonging to the catalytic converter and/or silencer, wherein the two flexible pipe members define a straight line which at least approximately intersects a virtual axis about which the engine casing can swivel during operation.
The invention furthermore relates to a motor vehicle having an exhaust system and having a vehicle body and an internal combustion engine, the engine casing of the latter being held on the vehicle body, wherein the exhaust is formed and is held on the vehicle body by retaining means in such a way that a straight line passing through the two pipe members at least approximately intersects the virtual axis about which the engine casing can swivel during operation.
It is also an object of the invention to provide a method for the formation of an exhaust system for a motor vehicle which has a vehicle body and an internal combustion engine with an engine casing and which has an exhaust connectable to the internal combustion engine and having a first flexible pipe member, a second flexible pipe member, connected to said first pipe member via a pipe, and at least one casing arranged downstream of said second pipe member and belonging to a catalytic converter and/or silencer, wherein a virtual axis is determined about which the engine casing swivels during operation, and wherein the exhaust is formed and arranged in such a way that a straight line passing through the two flexible pipe members at least approximately intersects the virtual axis.
According to the invention, two flexible pipe members connected to one another by a pipe define a straight line which passes through the two flexible pipe members, for example approximately through their centers, and at least approximately intersects the virtual axis of rotation and/or pivot axis. The position and direction of the virtual axis are dependent on the formation of the internal combustion engine and on the retaining means mentioned with which the engine casing is held on the vehicle body with vibration damping. The position and direction of the virtual axis may also be dependent on the condition of the motor vehicle and of the internal combustion engine, for example on the temperature of the internal combustion engine and/or on the speed of the engine shaft and/or the power instantaneously generated by the internal combustion engine. Furthermore, changes in power may result in a slightly rolling movement of the engine casing. Moreover, the vibration may also cause more or less linear movements of the engine casing so that swivel movements and linear movements are superposed. In addition, driving of the vehicle may also cause movements of the engine casing. Thus, owing to changes in power and/or oscillations, the engine housing often executes not pure swivel movements but only approximately swivel movements about a virtual axis. Furthermore, the position and direction of the virtual axis may also be dependent to a slight extent on the swivel angle or on the amplitude of a swivel movement which has just occurred and/or on the instantaneous swivel position of the engine casing. The positions and shapes of the flexible pipe members may also be dependent on the condition of the internal combustion engine and of the exhaust system, in particular on the temperature of the exhaust. However, the position and direction of the virtual axis can be determined experimentally for a specific condition of the motor vehicle and internal combustion engine, for example for a stationary vehicle after reaching the normal mean operating temperature of the engine at a mean engine power and for a mean swivel position of the engine casing. The flexible pipe members can then be arranged, according to the invention, in such a way that the straight line passing through the flexible pipe members, for example approximately through their centers, at least approximately and, for example, exactly intersects the virtual axis in a specific condition of the motor vehicle, of the internal combustion engine and of the exhaust system—for example with a stationary vehicle, c
Alexnat John W. Jörg
Steenackers Pieter Delfina
Dickson Paul N.
Scambia Industrial Developments AG
Sidley Austin Brown & Wood LLP
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